Beam deflector for cathode-ray tubes



y 20, 1952 M. EMMER ETAL 2,597,465

BEAM DEFLECTOR FOR CATHODE-RAY TUBES Fiied March 25, 1951 2 SHEETS.SHEET l INVENTORS fit/fan Emmer y Jdmes Zia/add M y 20, 1952 M. EMMER ETAL 2,597,465

BEAM DEFLECTOR FOR CAJHODE-RAY TUBES Filed March 25, 1951 2' SHEETS-SHEET 2 INVENTORS mum,

Patented May 20, 1952 UNITED STATES PATENT BEAM DEFLECTOR FOR CATHODE-RAY TUBES Milton Emmer and James Edward Henschel, Brooklyn, N. Y.

Application March 23, 1951, Serial No. 217,142

13 Claims. 1

The present invention relates to beam deflectors, especially those of the type associated with ion traps for cathode ray tubes.

The term cathode ray tube as used herei is intended to be generic, including all tubes which involve the use of a beam of electrons produced by an electron gun or similar device. The term is intended to include, for example, a television picture tube.

Cathode ray tubes commonly include electron guns which project a beam of electrons or cathode rays toward a target or a fluorescent screen. Such beams inherently include not only electrons but ions which may be produced in various ways, for example, by collision of the electrons with gas molecules. If such ions reach the target or screen, they may combine chemically with the material of the screen, causing it to lose its fluorescent characteristics. Such a phenomenon is referred to in the case of television picture tubes as an ion burn. It is common to prevent such ion burns by constructing the tubeso as to trap the ions and to prevent their reaching the target or screen. The trapping of the ions may be accomplished by constructing the electron gun so that it discharges the beam at an angle to the axis of the tube. The beam then passes a magnetic beam deflector which deflects the beam through a small angle so as to direct it toward a trap plate having an aperture in its center. Since the ions are heavier than the electrons, they are not deflected through the same angle by the magnetic beam deflector, but are instead deflected through a somewhat smaller angle. If

the beam deflector is properlypositioned with respect to the path of electron beam, then the 1 beam of electrons will proceed through the aperture in the trap plate, while the ions impinge on the plate and are there collected.

The beam deflector may be located outside th glass wall of the tube, since its magnetic field will be effective through the glass. It is highly desirable that the beam deflector be mounted outside of the tube so that it may be adjusted to insure that the electron beam passes through the aperture in the trap plate. Such beam deflectors commonly comprise one or more permanent magnets and suitable supporting structure by which the magnets may be adjustably positioned onthe neck of the tube. It is with such beam deflectors that the present invention is concerned.

An object of the invention is to provide a magnetic beam deflector which is easy and economical to manufacture. Another object is to provide a beam deflector which is compact and structurally simple.

A further object is to provide a beam deflector which will produce a concentrated magnetic field extending substantially diametrically across the neck of the tube.

Another object is to provide a beam deflector which may be adjustably positioned on the surface of a glass tube without scratching or damaging' the glass. Another object is to provide a beam deflector which may be readily installed or removed from a tube, even though the tube may have a base of greater diameter than the glass neck which carries the beam deflector.

The foregoing and other objects of the invention are attained by constructing the beam deflector in the form of an annulus having two or more segments. These segments are formed of nonmagnetic material substantially softer than glass, preferably moldable plastic material. The segments are provided with interfitting ends and are held in frictional engagement with the neck of the tube by means of an encircling tension band which may take the form of a rubber ring. The segments have their edges bevelled so as to slide readily over the tube. Each segment has a recess on its inner surface for receiving a magnet. The

recess is deeper than the magnet, so that the magnet does not touch the tube.

The'magnets may be provided with pole pieces so as to form two semi-circular magnetic members with their adjacent ends slightly spaced apart. When such magnets are arranged so that the adjacent ends are of like polarity, then they provide a concentrated magnetic field extending substantially diametrically across the neck of the tube.

In the accompanying drawings:

Fig. 1 is an elevational view of the inside surface of one segment of one form of beam deflector constructed in accordance with the present invention.

Fig. 2 is a side view of the segment shown in Fi 1.

Fig. 3 is a plan view of a rubber ring which forms part of a complete beam deflector.

Fig. 4 is an assembly view showing a complete beam deflector mounted on the neck of a cathode ray tube.

- Fig. 5 is a somewhat diagrammatic elevational view of a complete television picture tube, illustrating the relationship of the beam deflector, the tube base and the focusing coils.

Fig. 6 is an elevational view similar to Fig. 1, showing a modified form of beam deflector embodying our invention.

Fig. 7 is an assembly view showing a complete beam deflector of the type shown in Fig. 6, partly broken away.

Fig. 8 is an assembly view showing another modified form of a beam deflector embodying our invention.

Figs. 1 to 5 The complete beam deflector, best seen in Fig. 4, includes a pair of substantially semi-annular segments I, which are held in frictional engageglass engaging surfaces of the segments Iare bevelled, as shown at 3, as an aid in preventing damage to the glass and in sliding the beam deflector over the base of the tube. V

Each segment is provided with a central axially extending recess 4 in itsinner surface, for receiving a permanent magnet 5; The recess 4 is deeper than-the thickness of the-magnet 5, so 'thatthe magnet does not touch the surface of the glass tube. The magnet 5 may be cemented in place in the recess 4. The inner surface of the segments I may be hollowed out, as shown at 6, to save material. Y I

The segments I are provided with in terfitting end surfaces comprising substantially radial plane surfaces 8, one of which is provided with-a projecting pin 9, formed integrally with the 588- ment 1. The other plane surface 8 is provided with a recess IQ for receiving the pin 9 of the other segment. r

It may be seen that if all the segments :Iand

the magnets 5 are assembled with the polarities of the magnets in the same direction with respect to the position of the pins 9 and sockets'III, that the assembly of any two segments will result in a structure wherein the magnet poles which-are diametrically opposite each other are of opposite :2

polarity. Such an arrangement of the poles is necessary, since if the polarities of the diametri' cally opposite poles of equal-stren th w re t e same; the fields would buck each otherandthe net field existing near the axis of the tube would a be very weak and substantially ineffective to deflect the electron beam.

Referring to Fig. 5, there is shown a television picture tube I I on which is mounted a beam deflector generally indicated at I2 and constructed Picture.

When the tube II is being mounted anddismounted on the chassis of the set, the neck Ila must be passed through the focusing coils l3. In order that the focusing coils may work as efficiently as possible, it is customary to make their internal diameter as small as possible while still permitting passage of the base Ila. Since the ouside diameter of the beam deflector islarger than the inside diameter of the focusing coils, the beam deflector must be removed over the'bas'e before the tube can be dismounted. Similarly, the beam deflector must be installed over the base after the neck of the tube is inserted through the focusing coils I3.

When using a beam deflector constructed in accordance with the present invention,it is simple to separate the two segments far enough to expand the annulus so that it passes readilyfover the base I Ia. Furthermore, the beam deflector is readily adjustable on' the internal surfaceof the tube and is firmly held in frictional engagement with that surface without damage to the surface. The pins {are made long enough so that the two' segments may be separated far enough to pass over the base without having the pins lose their engagement with their opposing sockets I0. A The segments are made with their end surfaces 8 separated by a distance slightly less than the periphery of a semi-circle, so that when the two segments are assembled on a tube as shown in Fig; 4, both segments snugly engage the tube surface; The radial end surfaces 8 are then spaced from each other, so that they do not interfere with the-"contact of the segments I against the glass surface of the tube.

.. Figs. 6 and? segmentsflfi Each segment I 4 is provided with an internal-groove I5, which is closed at its ends. In the-centef of the groove I5 is located a bar magnet I6; which is cemented in the groove. Between the ends of the bar magnet I6 and the ends of the g'r'o0ve-arelocated pole pieces I! of mag netichia'terial. This material may be a mixture of iron nimgssnd shellac, or some other magnetic powdered material mixed with a suitable binder, orit may baa-powdered and sintered magnetic material. --Instead of using a plastic mixture, bars-of magnetic material may be used as pole piecesfi' In the-embdimentof Figs. 6 and 7, each of the segments carries a magnetic element consisting of'onemagnet and two pole pieces. This magnetic element defines a. magnetic circuit having a semi-annular portion of magnetic material and a "diamet'rical portion extending through the space between the ends of the semi-annular porti0n-.' I1 T *When the two segments I4 are assembled on the neck I Ib oi' a cathode ray tube, as shown in Fig.7, the segments are arranged with their magnets in opposition. In other words, the north pole piece of; one segment isplaced adjacent the north polei-piece-ofthe other segment. This arrangement allows the diametrical portions of the magnetici circuits- 0f the two magnetic elements to aid each other so as-to produce a concentrated magneticfleld shown at I8, which extends diametrically across the neck III) of the tube with little or no spreadingor-distortion. It has been found that 'sucha magnetic field is very desirable in a beam-deflector, since its effect on the beam-may be more 'precisely controlled than is the case with other field configurations.

Each segment I4-is provided at each end with a; ;projection I} and a recess 20. By arranging thetwo projections in this manner, it can be assured that-if the magnets I 6 are all inserted with the proper polarity in relation to the projections I9 and recess 20, that the complete beam deflectors. when assembled, will have their magnetic polarities extending in the proper directions.

1 Thereis' shown in this figure another modified form of 'bea-m deflector embodying the invention. This beam deflector includes two segments 2I and 22'. The segment 2| carries a magnet 23, there being no magnet in the segment 22. Pole pieces-flof-plastic magnetic material are provided; similar 'to-the pol'e pieces H of Figs. 6 and "7. There arealso provided pole piece extensions 25, which project circumferentially beyond the ends of the segment 2 I. This arrangement of the pole pieces does not produce a concentrated magnetic field configuration as the arrangement of Figs. 6 and 7, but nevertheless has an advantage of simplicity and economy of construction.

We claim:

1. A beam deflector for a cathode ray tube, comprising an annulus formed by a plurality of segments having interfitting end portions and adapted to encircle the neck of a cathode ray tube, a yieldable tension band encircling said segments to retain them frictionally in place on said tube neck, and a permanent magnet carried by one of said segments.

2. A beam deflector for cathode ray tubes as defined in claim 1, in which said segments are formed of non-magnetic material substantially softer than glass.

3. A beam deflector for cathode ray tubes are defined in claim 1, in which said segments are formed of moldable plastic material.

4. A beam deflector for cathode ray tubes as defined in claim 1, in which said annulus comprises two substantially semi-annular segments.

5. A beam deflector for cathode ray tubes as defined in claim 1, in which the edges of the segment surfaces which engage the tube are bevelled to aid the removal of the annulus over the base of the tube.

6. A beam deflector for cathode ray tubes as defined in claim 1, in which the segment carrying the magnet has in its inner surface a magnet receiving recess deeper than the thickness of the magnet, so that the magnet does not contact the surface of the tube.

7. A beam deflector for cathode ray tubes as defined in claim 1, in which said interfitting end portions comprise a pin projecting from one end of each segment and a pin-receiving socket in the other end.

8. A beam deflector for cathode ray tubes as defined in claim 1, in which said band is sufliciently yieldable to permit separation of the segments far enough for installation or removal of the annulus over a tube base of larger diameter than the tube neck.

: 9. A beam deflector for cathode ray tubes as defined in claim 1, in which said interfitting end portions are substantially radial plane surfaces, with a pin projecting from the surface at one end and a pin-receiving socket in the surface at the other end, and said segments are slightly shorter than the length required to form a complete annulus, so that when assembled on a tube, said plane surfaces are slightly spaced.

10. A beam deflector for cathode ray tubes as defined in claim 1, in which said interfitting end portions comprise a projection on one end of each segment and a projection receiving recess on the opposite end, said projections being long enough to remain in engagement with the cooperating recesses during the segment separation required for installation or removal.

11. A beam deflector for a cathode ray tube, comprising an annulus formed by two substantially semi-annular segments of moldable plastic material and adapted to encircle the neck of a cathode ray tube, said segments having interfitting end portions in the form of substantially radial plane surfaces with a pin projecting from the surface at one end and a pin-receiving recess in the surface at the other end, said segments having bevelled edges on the tube-engaging surfaces and each having a central, axially extending recess for receiving a bar magnet, a magnet in each said recess, said recesses being deeper than the magnets so that the magnets do not engage the tube, said segments having a central peripheral groove in their outer surface, and a yieldable tension band in said groove for holding said segments assembled as an annulus.

12. A beam deflector for a cathode ray tube, comprising an annulus formed by two substantially semi-annular segments of moldable plastic material and adapted to encircle the neck of a cathode ray tube, said segments having interfitting end portions in the form of substantially radial plane surfaces with a pin projecting from the surface at one end and a pin-receiving socket in the surface at the other end, said segments having bevelled edges and each having a central, axially extending recess for receiving a bar magnet, a magnet in each said recess, said recesses being deeper than the magnets so that the magnets do not engage the tube, said magnets being arranged with their polarities in the same direction with respect to the pin and socket of their associated segment, and a yieldable tension band for holding said segments assembled as an annulus.

13. A structure for supporting a permanent magnet beam deflector on the neck of a cathode ray tube, comprising a plurality of annular segments having interfitting end portions and cooperating to form a substantially complete annulus when assembled with said ends interfitted, said annulus being adapted to encircle the neck of a cathode ray tube, and a yieldable tension band encircling said segments to retain them frictionally in place on said tube neck, at least one of said segments having a recess for receiving a permanent magnet.

MILTON EMMER. JAMES EDWARD HENSCHEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,102,421 Kuehni Dec. 14. 1937 2,211,613 Bowie Aug. 3, 1940 2,456,474 Wainwright Dec. 14, 1948 2,460,609 Torsch Feb. 1, 1949 2,499,065 Heppner 1. Feb. 28, 1950 2,500,455 Fisher Mar. 14, 1950 2,513,929 Gethmann July 4, 1950 2,522,872 Heppner Sept. 19, 1950 2,525,919 Loughren Oct. 17, 1950 2,539,156 Ostreicher Jan. 23, 1951 2,542,924 Heppner Feb. 20, 1951 2,544,875 Bennett Mar. 13, 1951 2,544,898 Obszarny et al Mar. 13, 1951 

